Capacitance-voltage and impedance characteristics of field-effect EIS sensors functionalised with polyelectrolyte multilayers

Impedance-spectroscopy (IS) and capacitance-voltage characteristics of a field-effect-based electrolyte-insulator-semiconductor (EIS) sensor functionalised with polyelectrolyte (PE) multilayers have been investigated. The PE multilayers were obtained using the layer-by-layer technique by a consecutive adsorption of positively charged (poly(allylamine hydrochloride)) (PAH) and negatively charged (poly(sodium 4-styrene sulfonate)) (PSS) on a p-Si-SiO2 structure. Alternating shifts in the impedance and capacitance-voltage curves have been observed after the adsorption of each polyanion and polycation layer, respectively. The effects of the number of the adsorbed PE layers and polarity of the outermost layer on the impedance and capacitance-voltage curves are discussed. (C) 2007 Elsevier Masson SAS. All rights reserved

pH and ion sensitivity of a field-effect EIS (electrolyte-insulator-semiconductor) sensor covered with polyelectrolyte layers

Field-effect capacitive EIS (electrolyte-insulator-semiconductor) sensors have been utilised for a label-free electrical monitoring of the layer-by-layer adsorption of polyelectrolyte multilayers (PEM). Anionic poly(sodium 4-styrene sulfonate) and cationic poly(allylamine hydrochloride) have been used as model system. The effect of the number of PEMs and polarity of the terminating layer on the sensor signal have been investigated. In addition, pH and ion sensitivity of EIS sensors covered with PEM have been studied by constant-capacitance method. Alternating potential shifts, having a tendency to decrease with increasing the number of PE layers, have been observed after the adsorption of each polycation and polyanion layer. The possible mechanisms for the sensor response are discussed

Label-free detection of charged macromelecules by using a field-effect-based sensor platform: Experiments and possible mechanisms of signal generation

The possibilities and limitations of a direct electrical detection of charged macromolecules using a field-effect-based sensor platform is evaluated, mainly focusing on capacitive EIS (electrolyte-insulator-semiconductor) devices. The experimentally obtained results on the detection of DNA immobilisation and hybridisation as well as the monitoring of layer-by-layer adsorbed charged polyelectrolyte (PE) multilayers have been discussed by using two basic possible mechanisms of signal generation, namely the intrinsic charge of the macromolecules and the charge redistribution within the intermolecular spaces or in the multilayer. The effects of the layer-by-layer adsorption conditions (unbuffered and pH buffer solution), and the number and polarity of charged layers on the sensor response have been systematically investigated by means of capacitance-voltage (C-V), constant-capacitance (ConCap) and impedance spectroscopy (IS) methods